I don't know about a myth, the Searle system of the Savage autopistols assumed that torque against the rifling would hold the barrel a bit. But it was only 5 degrees rotation and was at best a slightly delayed blowback. Not to be confused with the large angle cam track rotation of the other makes listed.

The theoretical greater accuracy of the rotating barrel appears to remain undeveloped. There was a target model of the French PA15 with longer barrel and adjustable sights, but I have never seen a report on actually shooting one.

I have seen old reports to the effect that the Colt-Browning "parallel ruler" guns of 1900-1907 were very accurate as production model pistols go. Possibly even to a level requiring special attention to accurize a tipping barrel 1911 or successor.